Light-emitting apparatus and method for forming the same

Abstract

In a light-emitting apparatus, a face of a substrate on which a light-emitting device is formed is an uneven surface having a plurality of asperities. The mean spacing Sm of adjacent asperities or the mean spacing S of peaks of adjacent projections of the asperities is no less than three times the longest wavelength of light generated by a light-emitting layer and no more than two hundred times the longest wavelength. The arithmetic mean slope Δa of the uneven surface is in a range between 4° and 30°, inclusive. Therefore, the apparatus emits substantially a greater amount of light from a light extraction side and has less brightness unevenness than a light-emitting apparatus with no uneven surface.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a light-emitting apparatus having a substrate on which a light-emitting device is formed. The light-emitting device is an organic electroluminescent device (organic EL device) or an inorganic electroluminescent element (inorganic EL elements). Such a device has a light-emitting layer held between a pair of electrodes. The present invention also pertains to a method for forming the apparatus.[0002]Lighting systems and displays using a light-emitting apparatus such as an organic electroluminescent apparatus (organic EL apparatus) and an inorganic electroluminescent apparatus (inorganic EL apparatus) have been proposed.[0003]Such light-emitting apparatuses are known for low extraction efficiency. That is, the ratio of the light that is extracted outside from the apparatus to the light generated by a light-emitting layer is low. This is because layers forming a light-emitting apparatus have different refractive indices.[0...

AI Technical Summary

Benefits of technology

[0018]Further, a third objective of the present invention is to provide a light-emitting apparatus that, when used as a reflection plate, not only prevents specular reflection, but also has a high brightness in a specific direction when receiving light in a direction of an hypothetical light source. The present invention also pertains to a method for forming such an apparatus.

Problems solved by technology

Such light-emitting apparatuses are known for low extraction efficiency.

In these cases, however, when the light-emitting layer is not producing light, specular reflection of external light occurs.

However, as in the first prior art, forming an uneven surface having asperities on the substrate and forming light-emitting device on the uneven surface does not necessarily improve the extraction efficiency.

Also, depending on the shapes of the asperities, the following problems occur.

Further, the phenomenon causes a significant amount of current to pass through specific portions of the light-emitting layer 211, and thus shortens the lifetime of these portions.

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